Collision prevention control apparatus

ABSTRACT

According to one aspect of the disclosure, a collision prevention control apparatus is provided which includes an image sensor that detects an object near the vehicle; a radar sensor that detects the object near the vehicle; and a controller that, if only one of the sensors, among the image sensor and the radar sensor, detects the object, determines reliability of the other sensor, and changes, based on the determined reliability, a way of performing a collision prevention control for preventing a collision with the object detected by the one of the sensors.

FIELD

The disclosure is related to a collision prevention control apparatus.

BACKGROUND

Japanese Laid-open Patent Publication No. 2005-239114 (PatentDocument 1) discloses a traveling support device in which an obstacledetection result by radar (millimeter wave) and the obstacle detectionresult by the image recognition are collated to include a case detectedby both of the results and cases detected by respective ones of theresults, and a starting condition of the traveling support control ischanged according to the included results.

However, according to the configuration disclosed in Patent Document 1described above, a control condition of the traveling support control isnot determined, if only one of the image sensor and the radar sensordetects the obstacle, based on the reliability of the other sensor.

Therefore, according to the disclosure, it an object to provide acollision prevention control apparatus that, if only one of an imagesensor and a radar sensor detects an object, can consider reliability ofthe other sensor to perform collision prevention control related to theobject.

SUMMARY

According to one aspect of the disclosure, a collision preventioncontrol apparatus is provided, comprising:

an image sensor that detects an object near a vehicle;

a radar sensor that detects the object near the vehicle; and

a controller that, if only one of the sensors, among the image sensorand the radar sensor, detects the object, determines reliability of theother sensor, and changes, based on the determined reliability, a way ofperforming a collision prevention control for preventing a collisionwith the object detected by the one of the sensors.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a configuration of a collisionprevention control apparatus 1 according to an embodiment.

FIG. 2 is an example of a flowchart of a process executed by a vehiclecontrol ECU 10.

FIG. 3 is another example of a flowchart of the process executed by thevehicle control ECU 10.

FIG. 4 is another example of a flowchart of the process executed by thevehicle control ECU 10.

DESCRIPTION OF EMBODIMENTS

In the following, embodiments will be described with reference to theaccompanying drawings.

FIG. 1 is a diagram illustrating a configuration of a collisionprevention control apparatus 1 according to an embodiment. It is notedthat connection ways between elements in FIG. 1 are arbitrary. Forexample, the connection ways may include a connection via a bus such asa CAN (controller area network), etc., an indirect connection viaanother ECU, etc., a direct connection, and a connection that enableswireless communication.

The collision prevention control apparatus 1 includes a vehicle controlECU (Electronic Control Unit) 10. The vehicle control ECU 10 may beformed by a processor that includes a CPU. Functions of the vehiclecontrol ECU 10 (including functions described hereinafter) may beimplemented by any hardware, any software, any firmware or anycombination thereof. For example, any part of or all the functions ofthe vehicle control ECU 10 may be implemented by an ASIC(application-specific integrated circuit), a FPGA (Field ProgrammableGate Array) or a DSP (digital signal processor). Further, the vehiclecontrol ECU 10 may be implemented by a plurality of processors.

The vehicle control ECU 10 is connected to a forward radar sensor 16 andan image sensor 18.

The forward radar sensor 16 detects a state (object information) of anobject (a preceding vehicle, etc., for example) in front of a hostvehicle using an electric wave (millimeter wave, for example), a lightwave (laser, for example) or an ultrasonic wave as a detection wave. Theforward radar sensor 16 detects information which represents arelationship between the object and the host vehicle such as a relativespeed, a relative distance and a direction (a lateral position) withrespect to the host vehicle, for example, at a predetermined cycle. Itis noted that if the forward radar sensor 16 is a millimeter wave radarsensor, the millimeter wave radar sensor may be of an electroniccontrolled scanning type, for example. In this case, the relative speedof the object is detected using a Doppler frequency (frequency shift) ofthe electric wave, the relative distance of the object is detected usinga delayed time of the reflection wave, and the direction of the objectis detected based on a shift difference of the received waves between aplurality of reception antennas. The object information thus obtained istransmitted to the vehicle control ECU 10 at a predetermined cycle. Itis noted that any functions of the forward radar sensor 16 (a functionof calculating a position of the object, for example) may be implementedby the vehicle control ECU 10.

The image sensor includes a camera, which includes imaging elements suchas CCDs (charge-coupled device), CMOSs (complementary metal oxidesemiconductor), etc., and an image processor to recognize the state ofthe object. A detection area of the image sensor 18 (i.e., an imagingarea or an image processing area of the camera) is in front of the hostvehicle, as is the case with the detection area of the forward radarsensor 16. The detection area of the image sensor 18 is partially orcompletely overlapped with the detection area of the forward radarsensor 16. In other words, the image sensor 18 and the forward radarsensor 16 include a common detection region.

The camera of the image sensor 18 may be a monocular camera or a stereocamera. The image sensor 18 detects, based on an image recognitionresult, the information which represents a relationship between theobject and the host vehicle such as a relative speed and positioninformation of the object with respect to the host vehicle, for example,at a predetermined cycle. The position information of the objectincludes information related to the position (distance) of the object inthe back-and-forth direction of the host vehicle, and informationrelated to the lateral position of the object in the lateral direction(width direction). The lateral position of the object may be calculatedbased on a center position of a pixel group related to the object in thelateral direction. Alternatively, the lateral position of the object maybe calculated as a range between a left end lateral position and a rightend lateral position. The object information thus obtained with theimage sensor 18 may be transmitted to the vehicle control ECU 10 at apredetermined cycle. It is noted that the image processing function ofthe image processor (a function of calculating a position of the object,for example) may be implemented by the vehicle control ECU 10.

The vehicle control ECU 10 is connected to an alert output device 30 anda brake device 40. The vehicle control ECU 10 performs collisionprevention control via the alert output device 30 and/or the brakedevice 40. The collision prevention control includes an alert outputcontrol implemented by using the alert output device 30 and an automaticbrake control implemented by using the brake device 40.

The alert output device 30 includes a display device such as a meter,etc., or an audio generation device such as a speaker, a buzzer, etc.,for example.

The brake device 40 generates a brake force at the respective wheels ofthe vehicle. The brake device 40 may include actuators and valves forcontrolling wheel cylinder pressures. The oil hydraulic circuit of thebrake device 40 may have such a configuration that it can increase thewheel cylinder pressures regardless of a brake pedal operation amount bya driver (i.e., a configuration that can implement automatic brakecontrol). Typically, the oil hydraulic circuit of the brake apparatusmay include a high-pressure source (a pump for generating thehigh-pressure oil and an accumulator, for example) other than a mastercylinder. Further, such an oil hydraulic circuit that is typically usedin a brake-by-wire system such as an ECB (Electric Control Brakingsystem) may be adapted.

FIG. 2 is an example of a flowchart of a process executed by a vehiclecontrol ECU 10. The process routine illustrated in FIG. 2 may beinitiated, during the traveling of the vehicle, if an object is detectedin the common detection region of the forward radar sensor 16 and theimage sensor 18 and by the forward radar sensor 16 and/or the imagesensor 18.

In step S200, the vehicle control ECU 10 calculates reliability of theforward radar sensor 16 and reliability of the image sensor 18. Here,the vehicle control ECU 10 calculates, as examples of the reliability ofthe forward radar sensor 16 and the reliability of the image sensor 18,a number of items of effective data nrd (referred to as “effective datanumber nrd”, hereinafter) of the forward radar sensor 16 and a number ofitems of effective data ncd (referred to as “effective data number ncd”,hereinafter) of the image sensor 18.

The effective data of the forward radar sensor 16 is data whosereception level of a reception wave related to a radar transmission waveis greater than or equal to a predetermined value, for example. In otherwords, the effective data of the forward radar sensor 16 is data ofreflection points, among the data of the reflection points received bythe forward radar sensor 16, whose reception level of the reception waverelated to a radar transmission wave is greater than or equal to apredetermined value and for which the distance information can becalculated. In this case, the effective data number nrd of the forwardradar sensor 16 corresponds to a number of the reflection points (i.e.,a number of peaks of the reception wave) in the detection area of theforward radar sensor 16 as a whole.

The effective data of the image sensor 18 is data (i.e., edge data)whose differential value in a differential image (differential in aconcentration between neighboring pixels) of the image data is greaterthan or equal to a predetermined value, for example. If the camera ofthe image sensor 18 is a stereo camera, the effective data may be dataof points (pixels) for which parallaxes (i.e., distances), which aregreater than or equal to a predetermined value, are detected. Further,if the camera of the image sensor 18 is a monocular camera, theeffective data may be data of points for which optical flows can bedetermined by determining corresponding points between images obtainedat different times. In these cases, the effective data number ncd of theimage sensor 18 corresponds to the number of these points in the imageas a whole.

In step S202, the vehicle control ECU 10 categorizes the detectedobjects into three types, “a fusion object”, “a radar only object” and“an image only object”, based on the object information obtained fromthe forward radar sensor 16 and/or the image sensor 18. The fusionobject is an object (the identical object) that can be detected by theforward radar sensor 16 and the image sensor 18. The radar only objectis an object that can be detected by only the forward radar sensor 16,among the forward radar sensor 16 and the image sensor 18. The imageonly object is an object that can be detected by only the image sensor18, among the forward radar sensor 16 and the image sensor 18.

In step S204, the vehicle control ECU 10 determines whether the detectedobject is a target for which the collision prevention control is to beperformed, that is to say, an obstacle whose probability of collisionwith the host vehicle is high, based on the object information from theforward radar sensor 16 and/or the image sensor 18. Various ways ofdetermining whether the detected object is an obstacle are known in afield of pre-crash safety and an arbitrary way may be used. For example,the vehicle control ECU 10 may calculate a TTC (Time to Collision)before the collision with the detected object, and determine that thedetected object is an obstacle if the candidate TTC is less than apredetermined value (1 s, for example). Then, the lateral position ofthe object may be considered. For example, if the object is locatedwithin a predetermined width with respect to the traveling direction ofthe host vehicle, it may be determined that the detected object is anobstacle. It is noted that TTC may be derived by dividing the relativedistance to the object by the relative speed with respect to the object.

In step S204, if the vehicle control ECU 10 determines that the detectedobject is an obstacle, the vehicle control ECU 10 categorizes theobstacle into “a fusion obstacle”, “a radar only obstacle” or “an imageonly obstacle” to go to step S206. It is noted that this categorizationis based on the categorization result of step S204. For example, if thedetected object is the fusion object and determined as an obstacle, thedetected object is categorized as a fusion obstacle. On the other hand,if it is determined that the detected object is not an obstacle, theprocess may return step S200 to repeat the process from step S200 at thenext process cycle.

In step S206, the vehicle control ECU 10 determines the categorizationresult of step S204 to go to step S208, S210 or S214 according to thecategorization result. Specifically, in the case of the fusion obstacle,the process goes to step S214; in the case of the radar alone obstacle,the process goes to step S208; and in the case of the image aloneobstacle, the process goes to step S210.

In step S208, the vehicle control ECU 10 determines whether theeffective data number ncd of the image sensor 18 is greater than orequal to a predetermined threshold NCD. The predetermined threshold NCDcorresponds to a lower limit of the effective data number ncd at whichit can be determined that the reliability of the image sensor 18 ishigh. The predetermined threshold NCD may be adapted based onexperimental data, etc. If the effective data number ncd of the imagesensor 18 is greater than or equal to the predetermined value NCD, theprocess goes to step 212, otherwise the process goes to step 214.

In step S210, the vehicle control ECU 10 determines whether theeffective data number nrd of the forward radar sensor 16 is greater thanor equal to a predetermined threshold NRD. The predetermined thresholdNRD corresponds to a lower limit of the effective data number nrd atwhich it can be determined that the reliability of the forward radarsensor 16 is high. The predetermined threshold NRD may be adapted basedon experimental data, etc. If the effective data number nrd of theforward radar sensor 16 is greater than or equal to a predeterminedthreshold NRD, the process goes to step 216, otherwise the process goesto step 214.

In step S212, the vehicle control ECU 10 performs the collisionprevention control for the radar only obstacle based on the obstacleinformation from the forward radar sensor 16 such that a collisionprevention capability by the collision prevention control is reduced. Inother words, the collision prevention capability is reduced with respectto the collision prevention capability in the case of an ordinarycollision prevention control for the radar only obstacle (see stepS214). The way of reducing the collision prevention capability may bearbitrary. For example, the reduction of the collision preventioncapability may be implemented by delaying a start timing of thecollision prevention control, making a control amount (the brake forceat the time of the automatic brake control) at the time of execution ofthe collision prevention control small, or changing a content of thecollision prevention control. Further, for example, according to theordinary collision prevention control, once the automatic brake controlis performed, the automatic brake control operated state continues untilthe vehicle stops (but the driver may cancel it), while, according tothe reduction of the collision prevention capability, even if theautomatic brake control is performed, the automatic brake controloperated state may be canceled if the object is not detectedsubsequently based on the object information from the forward radarsensor 16. Further, for example, according to the ordinary collisionprevention control, the alert output and the automatic brake control areperformed, while, according to the reduction of the collision preventioncapability, only the alert output, or only the alert output and a PBA(Pre-crash Brake Assist) may be performed. The PBA is a control forassisting a brake operation of the driver. For example, the PBA is acontrol that automatically increases the pressed amount of the brakepedal of the driver.

In step S214, the vehicle control ECU 10 performs the ordinary collisionprevention control based on the object information obtained from theforward radar sensor 16 and/or the image sensor 18. Specifically, thevehicle control ECU 10 performs the ordinary collision preventioncontrol for the radar only obstacle if the obstacle is the radar onlyobstacle (see “NO” in step S208), performs the ordinary collisionprevention control for the image only obstacle if the obstacle is theimage only obstacle (see “NO” in step S210), and performs the ordinarycollision prevention control for the fusion obstacle if the obstacle isthe fusion obstacle. The ordinary collision prevention control for theradar only obstacle is performed based on the obstacle information fromthe forward radar sensor 16, the ordinary collision prevention controlfor the image only obstacle is performed based on the obstacleinformation from the image sensor 18, and the ordinary collisionprevention control for the fusion obstacle is performed based on theobstacle information from the forward radar sensor 16 and the imagesensor 18. The ordinary collision prevention control for the radar onlyobstacle and the ordinary collision prevention control for the imageonly obstacle may be the same as the ordinary collision preventioncontrol for the fusion obstacle, or may have the reduced collisionprevention capability with respect to the ordinary collision preventioncontrol for the fusion obstacle. The way of reducing the collisionprevention capability is as described with reference to the process ofstep S212 but differs in the degree of the reduction. It is noted thatthe ordinary collision prevention control for the radar only obstacle,the ordinary collision prevention control for the image only obstacle,and the ordinary collision prevention control for the fusion obstaclemay differ in operation conditions, contents, etc., due to the fact thatthe object information available is different, respectively. Forexample, with respect to the ordinary collision prevention control forthe radar only obstacle, the lateral width of the object is not detectedby the forward radar sensor 16, and thus the lateral width of the objectcannot be considered to perform the control. In contrast, with respectto the ordinary collision prevention control for the image onlyobstacle, and the ordinary collision prevention control for the fusionobstacle, such a lateral width of the object can be considered toperform the control. On the other hand, there may be a case where theaccuracy of the object information of the image sensor 18 is worse thanthat of the forward radar sensor 16. Thus, the ordinary collisionprevention control for the image only obstacle may differ from theordinary collision prevention control for the radar only obstacle andthe ordinary collision prevention control for the fusion obstacle inthat a starting timing of the control is delayed or the automatic brakeis not operated.

In step S216, the vehicle control ECU 10 performs the collisionprevention control for the image only obstacle based on the obstacleinformation from the image sensor 18 such that the prevention capabilityby the collision prevention control is reduced. The way of reducing thecollision prevention capability is as described with reference to theprocess of step S212.

There may be a case where the forward radar sensor 16 detects ironplates for construction, steps on the road, etc., as an object. Incontrast, the probability that the image sensor 18 detects such steps onthe road as an object is low, because the image sensor 18 can recognizea height and a pattern of the object. On the other hand, there may be acase where the image sensor 18 erroneously detects complicated patternson the road (grid patterns, for example) as a 3D object, and erroneouslydetects a pattern that is similar to a pedestrian, as a pedestrian. Incontrast, this error does not hold true for the forward radar sensor 16.Thus, according to the process illustrated in FIG. 2, the ordinarycollision prevention control is performed if the same object is detectedby the forward radar sensor 16 and the image sensor 18, so that thecollision prevention control can be performed with high reliability.

However, the collision prevention control is suppressed evenly if theobject is detected by only one of the forward radar sensor 16 and theimage sensor 18, and the collision prevention control may be suppressedat unnecessary scenes. For example, the object may not be detected bythe image sensor 18 even if the object really exists, when sun light isreceived directly by the image sensor 18 or the light is insufficient ina dark circumstance. Further, the object may not be detected by theforward radar sensor 16 even if the object really exists, when atransmission coefficient of the electrical radiation is reduced due tosplashes (sleet, etc.) on a front surface of the sensor. In these cases,if the collision prevention control is suppressed evenly, the collisionprevention control may be suppressed even if the object really exists.

According to the process illustrated in FIG. 2, if the object isdetected by only one of the forward radar sensor 16 and the image sensor18, the reliability of the other sensor is determined in step S208 andstep S210, and a way of performing the collision prevention control(collision prevention capability) is changed based on the determinedreliability. With this arrangement, if the object is detected by onlyone of the forward radar sensor 16 and the image sensor 18, thecollision prevention control with an appropriate collision preventioncapability can be performed.

Specifically, for example, it can be determined that the reliability ofthe image sensor 18 is high if the effective data number ncd of theimage sensor 18 is greater than the predetermined threshold NCD, even ifthe obstacle is the radar only obstacle. The probability that the radaronly obstacle is not a 3D object in reality is high, because the radaronly obstacle is not detected by the reliable image sensor 18. Thus, inthis case, the collision prevention control for the radar only obstacleis suppressed (see step S212). On the other hand, if the effective datanumber ncd of the image sensor 18 is less than or equal to thepredetermined threshold NCD, the probability that the object is notdetected temporarily by the image sensor 18 due to the backlight, thedark circumstance, etc., is high. In other words, it is not always acase that “the probability that the object exists is low because of thefact that the image sensor 18 does not detect the object”. Thus, in thiscase, the ordinary collision prevention control for the radar onlyobstacle is performed (see step S214).

Similarly, the reliability of the forward radar sensor 16 is high if theeffective data number of nrd the forward radar sensor 16 is greater thanthe predetermined threshold NRD even if the obstacle is the image onlyobstacle. The probability that the image only obstacle is not a 3Dobject in reality is high, because the image only obstacle is notdetected by the reliable forward radar sensor 16. Thus, in this case,the collision prevention control for the image only obstacle issuppressed (see step S216). On the other hand, if the effective datanumber nrd of the forward radar sensor 16 is less than or equal to thepredetermined threshold NRD, the probability that the object is notdetected temporarily by the forward radar sensor 16 due to the splashes(sleet, etc.), etc., is high. In other words, it is not always a casethat “the probability that the object exists is low because of the factthat the forward radar sensor 16 does not detect the object”. Thus, inthis case, the ordinary collision prevention control for the image onlyobstacle is performed (see step S214).

FIG. 3 is another example of a flowchart of the process executed by thevehicle control ECU 10. The process illustrated in FIG. 3 differs fromthe process illustrated in FIG. 2 in that processes of steps S3071,S3072, S3091 and S3092 are added. Processes of steps S300 through S306,and S308 through S316 may be the same as the processes of steps S200through S206, and S208 through S216 illustrated in FIG. 2, respectively.

In step 3071, it is determined whether the image sensor 18 has afailure. There are various ways of determining the failure of the imagesensor 18, and an arbitrary way may be used. If the image sensor 18 hasa failure, the process goes to step S314, otherwise the process goes tostep S3072. It is noted that, if the image sensor 18 has a failure, aradar-only-mode may be formed as a failsafe mode in which the collisionprevention control is performed by using only the object informationfrom the forward radar sensor 16.

In step 3072, it is determined whether the image sensor 18 is in atemporary unused state. The temporary unused state of the image sensor18 may be formed if backlight due to the sun, high beams of an oncomingvehicle, rain drops on a front glass (detected by a rain sensor), arainy state, or a foreign substance on the front glass, etc., isdetected. If the image sensor 18 is in the temporary unused state, theprocess goes to step S314, otherwise the process goes to step S308. Itis noted that, similarly, if the image sensor 18 is in the temporaryunused state, the radar-only-mode may be formed as a failsafe mode inwhich the collision prevention control is performed by using only theobject information from the forward radar sensor 16.

In step 3091, it is determined whether the forward radar sensor 16 has afailure. There are various ways of determining the failure of theforward radar sensor 16, and an arbitrary way may be used. If theforward radar sensor 16 has a failure, the process goes to step S314,otherwise the process goes to step S3092. It is noted that, if theforward radar sensor 16 has a failure, an image-only-mode may be formedas a failsafe mode in which the collision prevention control isperformed by using only the object information from the image sensor 18.

In step 3092, it is determined whether the forward radar sensor 16 in atemporary unused state. The temporary unused state of the forward radarsensor 16 may be formed if the splashes, or a foreign substance on afront cover of the forward radar sensor 16, etc., is detected. If theforward radar sensor 16 is in the temporary unused state, the processgoes to step S314, otherwise the process goes to step S310. It is notedthat, similarly, if the forward radar sensor 16 is in the temporaryunused state, the image-only-mode may be formed as a failsafe mode inwhich the collision prevention control is performed by using only theobject information from the image sensor 18.

According to the process illustrated in FIG. 3, the same effects as theprocess illustrated in FIG. 2 can be obtained.

FIG. 4 is another example of a flowchart of the process executed by thevehicle control ECU 10. The process illustrated in FIG. 4 differs fromthe process illustrated in FIG. 2 in that processes of steps S4051 andS4052 are added. Processes of steps S400 through S404, S406 throughS412, and S416 may be the same as the processes of steps S200 throughS204, S206 through S212, and S216 illustrated in FIG. 2, respectively.

In step S4051, it is determined whether the obstacle is a stationaryobstacle. Whether the obstacle is a stationary obstacle may bedetermined based on a vehicle speed of the host vehicle or the objectinformation (relative speed of the obstacle). If the obstacle is astationary obstacle, the process goes to step S406, otherwise (i.e., inthe case of a moving obstacle) the process goes to step S4052.

In step S4052, the vehicle control ECU 10 performs the ordinarycollision prevention control for the moving obstacle based on the objectinformation obtained from the forward radar sensor 16 and/or the imagesensor 18. The ordinary collision prevention control may differ betweenthe case where the obstacle is the radar only obstacle, the case wherethe obstacle is the image only obstacle, and the case where the obstacleis the fusion obstacle. It is noted that the ordinary collisionprevention control for the moving obstacle may differ between the casewhere the moving obstacle is the oncoming vehicle and the case where themoving obstacle is the preceding vehicle.

In step S414, the vehicle control ECU 10 performs the ordinary collisionprevention control for the stationary obstacle based on the objectinformation obtained from the forward radar sensor 16 and/or the imagesensor 18.

According to the process illustrated in FIG. 4, the same effects as theprocess illustrated in FIG. 2 can be obtained. According to the processillustrated in FIG. 4, the same process as illustrated in FIG. 2 isperformed only if the obstacle is the stationary obstacle. Thus,according to the process illustrated in FIG. 4, the reduction degree ofthe collision prevention control for the image only obstacle and theradar only obstacle is changed only for the stationary object thateasily causes erroneous detections by the forward radar sensor 16 andthe image sensor 18. This is because the erroneous detections by theforward radar sensor 16 easily occur for the stationary object such assteps on the road, etc., and the erroneous detections by the imagesensor 18 easily occur for the stationary object such as patterns on theroad, etc., as described above.

Further, according to the process illustrated in FIG. 4, because it isdetermined whether the obstacle is a stationary obstacle, the ordinarycollision prevention control can be performed in an appropriate manner(a start timing, for example) according to whether the obstacle is astationary obstacle or not.

All examples and conditional language recited herein are intended forpedagogical purposes to aid the reader in understanding the inventionand the concepts contributed by the inventor to furthering the art, andare to be construed as being without limitation to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a showing of the superiority andinferiority of the invention. Although the embodiment(s) of the presentinventions have been described in detail, it should be understood thatthe various changes, substitutions, and alterations could be made heretowithout departing from the spirit and scope of the invention. Further,all or part of the components of the embodiments described above can becombined.

The present application is based on Japanese Priority Application No.2014-020672, filed on Feb. 5, 2014, the entire contents of which arehereby incorporated by reference.

What is claimed is:
 1. A collision prevention control apparatus,comprising: an image sensor that detects an object near a vehicle; aradar sensor that detects the object near the vehicle; and a controllerthat, when only a first one of the sensors, among the image sensor andthe radar sensor, detects the object, determines a reliability of dataobtained by a second one of the sensors, and changes, based on thedetermined reliability of the data obtained by the second one of thesensors, a performance of a collision prevention control for preventinga collision with the object detected by the first one of the sensors,wherein the controller changes the performance of the collisionprevention control such that a prevention capability by the collisionprevention control is reduced as the determined reliability of the dataobtained by the second one of the sensors increases.
 2. The collisionprevention control apparatus of claim 1, wherein the controllerdetermines the reliability of the data obtained by the second one of thesensors based on a number of items of effective data obtained by thesecond one of the sensors, and the number of items of effective datacorresponds to a number of reflection points whose reception levels arehigher than a predetermined strength, when the second one of the sensorsis the radar sensor, and corresponds to a number of pixels for whichedges or parallaxes are detected or optical flows can be determined,when the second one of the sensors is the image sensor.
 3. The collisionprevention control apparatus of claim 1, wherein, when only one of theimage sensor and the radar sensor detects the object, the controllerchanges the performance of the collision prevention control such thatthe prevention capability by the collision prevention control is reducedcompared to a case where both the image sensor and the radar sensordetect the object.
 4. The collision prevention control apparatus ofclaim 1, wherein, when only one of the image sensor and the radar sensordetects the object that is stationary, the controller changes, based onthe determined reliability of the data obtained by the second one of thesensors, the performance of the collision prevention control forpreventing the collision with the object that is stationary.